Probing collective Motions of Proteins and Hydration Dynamics in Aqueous Solutions by a Wide Range Dielectric Spectroscopy

Abstract

Conformational dynamics of proteins affect how biological molecules exert their function and regulate their biological processes. Studying the dynamics of proteins and their hydration allows us to analyze their functions in aqueous solutions. However, the strong absorption of water makes tracking collective mode changes challenging. Thus, we have developed a very sensitive dielectric megahertz-to-terahertz frequency-domain spectroscopy system to probe the hydration shells as well as large-scale dynamics of these biomolecules. Using this system, we explore the real and imaginary dielectric response of solvated biomolecules over a range of 50 MHz to 2 THz. We have chosen several proteins to provide a model system including bovine serum albumin (BSA), lysozyme, cytochome_c, and myoglobin proteins. We have compared the dynamics of proteins as well as their hydration water. We have deduced the dynamics and the hydration water of these proteins by comparing their real and imaginary dielectric response and hydration water relaxation times. Comparing these assets of various proteins in different classes helps us shed light on the macromolecular dynamics in a biologically relevant water environment.